Question

Sabendo que xy=12, quanto vale (x-y)²-(x+y)²?

Answer 1

$(x-y)*(x-y)-(x+y)*(x+y)=$

$[x^{2}-xy-xy+y^{2}]-[x^{2}+xy+xy+y^{2}]$

$x^{2}-xy-xy+y^{2}-x^{2}-xy-xy-y^{2}= -4xy$

$xy=12 .... 4*12=48$